The present invention relates to a camshaft assembly. In particular, the present invention is directed to a modular camshaft assembly that permits the formation of a camshaft and cam lobes from different materials and allows for adjustment of the cam lobes to vary valve timing.
The construction of the camshaft generally is comprised of a cylindrical main body and a plurality of individual cam lobes for the purpose aforenoted. A camshaft as used in automotive engines has typically been machined, shaped for its periphery (becoming a cam surface), using a dedicated machine tool tailored to achieve this end, known as a camshaft shaping or milling machine, or a camshaft shaper or miller. Alternatively, the camshafts can be cast such that the cams and other functional elements are cast integrally with the shaft in one piece. In either case, the manufacture can be complicated. Furthermore, the single piece construction of a camshaft represents a compromise in physical properties. It is desirable for the cam lobes to be wear resistant do to the interaction with other engine components, whereas, it is desirable for the shaft to have high strength and stiffness properties.
One approach to improve the physical properties of the camshaft assembly is to produce the cam lobes and shaft from different materials. A camshaft is called xe2x80x9cbuilt-upxe2x80x9d when the shaft body and the cams have been produced separately and wherein the essentially finished cams are fixed on the shaft body. Built-up camshafts, for example with a steel tube as the shaft body, can have various installed or attached parts, namely cams, sprocket mountings, sprockets, axial bearings, axial bearing shoulders, and signal emitters, or the like.
U.S. Pat. No. 2,791,916 entitled xe2x80x9cMulti-Cam Assembly With Replaceable Cam Unitsxe2x80x9d to Kintzing discloses a multi-cam assembly having replaceable cam units. Each cam unit includes a pair of interfitting parts.
U.S. Pat. No. 5,417,186 entitled xe2x80x9cDual-Acting Apparatus For Variable Valve Timing and the Likexe2x80x9d to Elrod et al discloses a camshaft having elongated splines extending along the shaft. A plurality of cam members are positioned along the shaft. Each cam member includes an aperture through which the shaft extends. The aperture includes complementary splines engaging the splines on the shaft to fix the position of the cam member with respect to the shaft.
U.S. Pat. No. 5,537,971 entitled xe2x80x9cModular Crankshaft and Connecting Rod Bearing Assemblyxe2x80x9d to Pong discloses a modular camshaft assembly having cam lobes that are stamped from sheet metal or made as powdered metal pressings. The cam lobes are then pressed onto a camshaft. The cam lobes frictionally engages the camshaft.
U.S. Pat. No. 5,887,557 entitled xe2x80x9cCamshaft With Drive, Bearing and Cam Elementsxe2x80x9d to Battlogg discloses a camshaft that is formed with two or more central parallel rods. The camshaft elements are mounted on the rods. A drive element is secured to the parallel rods to rotate the camshaft.
U.S. Pat. No. 5,307,708 entitled xe2x80x9cCamshaft for Controlling Valves in Internal Combustion Enginesxe2x80x9d to Matt, U.S. Pat. No. 5,738,052 entitled xe2x80x9cComposite Camshaft for Internal Combustion Enginexe2x80x9d to Meurer et al., U.S. Pat. No. 5,992,265 entitled xe2x80x9cBuilt-Up Camshaftxe2x80x9d to Klaar, German Patent Publications DE 41 21 951 C1, DE 37 17 190 C2 and DE 195 20 306 A1 disclose built-up camshafts in which cam discs are pressed onto a tubular shaft body and are additionally secured in a positive-locking manner in the direction of rotation by, for example, friction.
These camshaft assemblies, however, do not permit easy assembly such that the camshaft assembly can be varied for different engine configurations. Furthermore, these camshaft assemblies do not permit easy repair to replace a worn or damaged cam lobe.
It is therefore an object of the present invention to provide a modular camshaft assembly having optimized metallurgical properties, wherein different materials are used for different portions of the camshaft assembly for improved performance.
It is another object of the present invention to provide a modular camshaft assembly that permits repair or replacement of a worn or damaged part without replacing the entire camshaft assembly.
It is another object of the present invention to provide a modular camshaft assembly that permits adjustment of individual cam lobes to vary and/or adjust the orientation of individual lobes to vary the timing of individual intake and exhaust valves.
It is another object of the present invention to provide a modular camshaft assembly that provides for interchangeable lobes for varying the camshaft assembly for different engine configurations;
Additional objects and advantages of the invention are set forth, in part, in the description which follows, and, in part, will be apparent to one of ordinary skill in the art from the description and/or practice of the invention.
In response to the foregoing challenges, applicant has developed an innovative modular camshaft assembly for use with, for example, an engine. The modular camshaft assembly includes an elongated shaft, at least one cam lobe assembly, at least one spacer assembly, and a cam adapter assembly. Each cam lobe assembly is selectively secured to the elongated shaft. Each spacer assembly is secured to the elongated shaft, wherein the spacer assembly is selectively positioned adjacent the cam lobe assembly. The cam adapter assembly is secured to the elongated shaft. The cam adapter assembly is adapted to connect the modular camshaft assembly to a drive assembly.
In accordance with the present invention, the modular camshaft may further include at least one bearing assembly. The at least one bearing assembly may be formed with a ceramic material. Each bearing assembly is positioned on the elongated shaft.
In accordance with the present invention, the modular camshaft assembly may further include an adjustable cam lobe fastener assembly. The cam lobe fastener assembly secures each cam lobe assembly to the elongated shaft to prevent rotation of each cam lobe assembly with respect to the elongated shaft. In accordance with the present invention, the adjustable cam lobe fastener assembly may include a cam lobe fastener for securing each cam lobe assembly to the elongated shaft, and an adjustment assembly for adjusting the position of the cam lobe fastener with respect to the elongated shaft. The cam lobe fastener assembly may include a fastener pin, which engages a recess in the cam lobe assembly. The adjustment assembly may include a plurality of recesses on the elongated shaft. Each recess is adapted to receive the fastener pin. It is contemplated that multiple recesses may be provided for each cam lobe assembly such that the timing of the valve opening may be adjusted by locating the pin in a different recess.
The modular cam shaft assembly in accordance with the present invention may further include a fastener assembly secured to opposite ends of the elongated shaft to prevent removal of each cam lobe assembly, each spacer assembly, and the cam adapter assembly from the elongated shaft.
It is contemplated that the modular camshaft assembly will include multiple cam lobe assemblies spaced along the elongated camshaft. A cam lobe assembly will be provided for each intake valve and for each exhaust valve. At least one spacer will be used to permit proper spacing of the cam lobe assemblies along the elongated shaft. Furthermore, multiple bearings will be provided to permit rotation of the elongated shaft when connected to the engine.